It is known that, in particular with a view to a space rendezvous between an approaching space vehicle and an approached space vehicle, it is important to ascertain the current relative position and current relative natural path of the two space vehicles. Various procedures have been implemented to this end hitherto.
For example, a radar may be stowed aboard the approaching space vehicle. However, the mass, cost and electricity consumption of the radar are sizable, so that they constitute forbidding constraints in respect of certain space vehicles.
Furthermore, use can be made of the GPS (Global Positioning System) network of positioning satellites. However, this solution includes some unknowns related to the degree of ignorance about the performance and reliability characteristics of the GPS system. To be specific, the GPS process requires special equipment stowed on each of the space vehicles.
It is also possible to carry out sightings from the ground by radar or theodolites and orbit-plotting calculations in order to determine the sought-after speed and path. However, this results in a great dependency on the ground infrastructures and a high degree of inaccuracy for relative distances below 20 km.
The object of the present invention is to remedy these disadvantages. It relates to a system which is simple, reliable, robust, accurate, independent of ground infrastructures and which can be easily stowed aboard a space vehicle, being of low mass and consuming little electrical energy.